I don't know what you'd call these. They're really easy to make, so if you're contemplating having a go with Sculpey, or just looking for an idea for the kids to do with their Plasticene, then these are good fun and cute.
They are just a shaped blob (a little reminiscent of the Babapapa cartoon from my childhood) with beads for eyes and a smiley mouth pressed in using a curled piece of wire. These are pressed onto a smooth stone and if they pop off after cooking and cooling, can always be glued back on with UHU.
If you are too young to remember Babapapa, here's a pic and I expect clips of their genius can be found on youtube, the home of everything we thought (or hoped) we'd never see again!